Inertia controlled shock absorber system



Jan. 20, 1959 M. FuNKHoUsER ET AL Y2,869,685

INERTIA CONTROLLED SHOCK ABSORBER SYSTEM Filed April 11, 1955 2 Sheets-Sheet 1 Jan'. 20, 1959 M. FuNKHousER ET AL 2,859,685

INERTIA CONTROLLED SHOCK ABSORBER SYSTEM .Filed April 11, 1955 2 sheets-sheet 2 INVENToRs MEAP/cx FUNK/musee By HA/aoLD SHI/L TzE 9046' V. www

A TTOENE Y United States Patent O i" INERTIA CONTRLLED SHOCK ABSORBER SYSTEM Application April 11, 1955, Serial No. 500,462

S Claims. (Cl. ISS-87) This invention relates to a shock absorbing system, and a shock absorber for the same, adapted for use on motor vehicles to damp relative movements between the axle and the body of the vehicle.

It has been conventional practice in the shock absorber art to provide shock absorbers between the body and axle of a motor vehicle that damped relative movement between the car body and car axle in a manner that the damping is largely a compromise between the energy ab sorption requirements needed when the motor vehicle is passing over smooth roads and that needed when the vehicle is passing over rough roads. When a vehicle passes over choppy roads with little or no body movement, there is a large amo-unt of an axle movement of the vehicle that could be a free movement. Such a condition arises when the vehicle is passing over what is termed a corduroy road. The short choppy oscillations imparted to the vehicle axle by this type of road can largely be dissipated in the spring system for the vehicle without major damping action from the' shock absorber. At least this is true until the car body begins to swing in a synchronous motio-n. As soon as the car body begins to move, then additional energy dissipation must be taken on by the shock absorber.

In other words, so long as the car body of the vehicle rides relatively level, the shock absorber need not have a high degree of energy absorption. Rather, the unsprung weight, such as the axle and wheels of the vehicle can be left relatively free.

However, since the shock absorber is provided primarily for the purpose of giving a comfortable ride to the passengers of the vehicle, the movement of the car body i relative to the road over which the vehicle is traveling is that condition which should be most actively controlled. Thus, when the road conditions are such as to effect movement of the car body relative to the road, then the energy dissipation by the shock absorber must be greater to retard the movement of the car body in its up and down oscillating movement.

It is therefore an object of this invention toV provide a shock abso-rbing system adapted for use on motor vehicles wherein the shock absorber connected between the axle and body of a vehiclewill permit relatively free movement of the axle of theV vehicle relative to the body until the body begins movement as a result of the shock condition and thereafter additional resistance is applied to the shock absorber to increase the energy absorbed by the shock absorber.

It is another object of the invention to provide a shock absorbing system to accomplish 'the foregoing object wherein an inertia responsive mechanism controls the action of the shock absorber, the inertia responsive mechanism being in'turn responsive to car body movement to control the shock absorber in response to the car body absorber having a fluid pressure sensitive control device' that is adapted to change the energy absorption characteristics ot the shock absorber in response to changes in fluid pressure applied to the uid pressure sensitive control device, and to control the change in tluid pressure to the uid pressure sensitive control device of the shock absorber in response to a signal means external of the shock absorber and energized to regulate the sensitivity of the said device.

lt is another object of the invention to provide a shock absorber for accomplishing the foregoing object `wherein the energy absorbing mechanism of the shock absorber is carried on an operating rod that is provided with a longitudinally extending fluid conducting passage to effect transmission of uid under pressure from an external source to the liuid pressure sensitive control device to render it active and inactive in response to changes in fluid pressure as transmitted through the hollow operat ing rod of the shock absorber.

It is another object of the invention to provide a shock absorber for accomplishing the foregoing object wherein the energy absorbing mechanism of the shock absorber is carried on an operating rod that is provided with a longitudinally extending fluid conducting passage to conduct fluid under pressurev to the iluid pressure sensitive control device to render it active and inactive in response to changes in fluid pressure delivered thru the operating rod Figure l is a diagrammatic illustration of a shock ab v sorbing system for a motor vehicle showing the shock absorber and the `inertia control device for the same in cross section.

Figure 2 is a cross sectional view of a modified form of shock absorber that can be incorporated in the system shown in Figure l.

Figure 3 is a cross sectional View taken along line 3 of Figure 2. v

Inthis invention the shock absorber comprises a cylinder 10 having a piston 11 reciprocable in the cylinder. The piston 11 is carried on one end of an operating rod 12 that projects through a rod guide member 13 secured on one end of the cylinder 1i), and which closes that end of the cylinder. The operating rod 12 projects through the rod guide member 13 and is provided with a resilient the end cap 21 forms a reservoir chamber Z2 for hy` draulic fluid circulated in the working cylinder 10 in amanner hereinafter described.

The operating rod 12 carries a mounting tittingZS while i' the cap 21 carries a mounting fitting 24 whereby the y shock absorber can be connected between the body and axle of a motor vehicle, relative movement between the body and the axle` effecting reciprocation of the piston 1 1 in the cylinder 19.

The piston 11 comprises a cylindrical body member 25 that has a plurality of longitudinally extending pas-- sages 26 therein terminating in a recess chamber 27 ,atl

one end of the body 25. The recess chamber 27 is closed by` means of a cover plate 28 that has a central opening 29 through which hydraulic fluid llows through thepisttniv Patented Jan. 20, 1953 between. opposite ends of the cylinder 10. upon recipro cation of the piston 11 in the cylinder 10.

The cover plate 28 is provided with one or more orifice passages" and 34 to permit controlled'fiow ofy uid bythe orifice passages from the cylinder chamber 32on one side: of the piston to the cylinder chamber 33 onthe opposite side ofthe piston'. The orifice passages 30 areA closed by aY valve 31 to prevent ow of'hyd'raulic fluid from the cylinder'chamber 33 to the cylinder charlie ber 32.

The main flow passage 29 in the. piston 11 is controlled by aI valve pistonldtl' that seats upon4 a' valve seat'l provideda'round the' periphery of the opening 29. The Valve piston 40'islidesfwithin a Huid receiving chamber 42 disposed a'xiallyin the' piston' 11, an 0 ring seal 4f'31beingA provided between the piston valve. 40 and thewall vof the chamber42. A compression' spring 44 disposed betweenthe piston valvel 401 and the retainer member 45 normally urgesthe valve 40 upon its seat 41.

The operating rod 12 has a longitudinally extending fluid conducting passage 46 provided therein, and the retainer member 45 has the passage 47 to provide for. delivery ofl'uid under pressure into the receiving chamber 4t2. in the piston 11 in a manner hereinafter described.

The closure member 18 on the lower end of the cylinder 10 has' an axial bore 50 in which a valve S1 is slidably positioned; The valve 51 has an annular recess 52 to provide a chamber 53 in cooperation with the bore 50 inthe closure memberk 18. The chamber 53 is connected with a cylindrical. chamber 54 by means of a conduit passage 55. f

The-chamber 54 is' formed by means of a cylindrical tube 56 surrounding the cylinder 10 and projecting' over` the outer peripheries of the closure members 18 and 13 at'opposite ends of. the cylinder 10. O` ring seals 57 and 58`eng'age the cylinder 56 and thereby close the chamber 54.

The upper cylinder chamber 33 of the shock absorber connects. with the chamber 54 through means ofV a passage 60 provided in the upper end of the cylinder 10 whereby flow of fluid can be conducted from the cylinder chamber 33 through the passage 60y and the chamber 54, and through passage 55 to the chamber 53 around the valve 51 in the closure member l.

The valve 51 is encircled by a valve member 65 that closes a plurality of passages 66 disposed around the boreA 50. A light compression spring 67 is conned betweenV the valve member S1 and the valve member 65 to fretain the valve member 65 upon its seat 68 and retain the valve seat69 of the valve 51 seated on the edge periphery of the bore i) in the closure member 18.

On the compressionvstroke of the shock absorber just described, that is-when the piston 11. lmoves'. toward thev closure member. 18, the hydraulic fluid is placed under pressure in the cylinder chamber 32. The pressure of the fluid in the cylinder chamber 32 causes the valvemember 51 to move downwardly and thereby open the chamber S3 to the reservoir chamber 22.. As the piston 11 moves downwardly, the rst action of the. hydraulic uid placed under pressure in the chamber 32 is to pass` through the restricted orices 30 and 34valve 31 opening at this time. As the pressure in the cylinder chamber 32fcontinues to build. up as a'result of downward movement of the piston 11 toward the closure member 18,'the piston valve 40 will be lifted from its seat so that there is then amajor ow of hydraulic iluid from the cylinder i theorifices 30 and 34 and the valve member' tit)V provide' thedesired control over they fiow'of hydraulicuid 'from the cylinder chamber 32 into the cylinder chamber. 33 to effect the desired energy absorption resulting from the relative movements of the piston and cylinder of the shock absorber.

On the rebound stroke of the shock absorber, that is when the piston 11 is moving toward the closure member 13 and away from the closure member 18, the hydraulic fluid in the cylinder chamber 33 will be placed under pressure. As the uid is placed under pressure in the cylinder chamber 33, the effect of the pressure will be.: transmitted through the passage 60, the' chamber 54'v and the passage 55' tothe chamber 53I around thek valve 51 in the closure member 18. However, since the annular recess 52 forming a chamber 53 has equivalent areas exposed to the pressure of the hydraulic uid, the valve is hydraulically balanced and the spring 67 will thus hold the valve 51 in closed position as illustrated in Figure l'thereby preventing any tlow of hydraulic fluid from the' cylinder chamber 33 Vthrough'. the valve 51.

The hydraulic fluid under pressure inthe cylinder chamber 33 will thus be-required to flow through the orifice passages 34` in the head. of the piston 11'. Valve 31 in theV head 23 of the pistonV 11 isv closed atthis time; As the pressure continues to build up in. the cylinderV chamber 33, the effect ofthe pressure will react on theA reaction area 79 of` the valve 40' to raise it against the: pressure'of. the' spring 44y and thereby allow ow' of. hydraulicI fluid. from the cylinder chamber 33 intothe.l cylinder chamber 32 under control ofthe oriices 34; and the valvel 40.

As'the pistonllly moves away from the closurefmcmber: 18,. the volume of. hydraulicl fluid transferredf from: the' chamberV 33' tothechamber 32 isless thanthe'increasingvolume ofl the chamber 32.' Thus at this time the valve: member 65 raises againstI the light pressure ofthe spring 67 to permit hydraulic fluid to ow through the passages S6-into thecylinder chamber 32 from the reservoir 22 to retain thecylinder chamber 32V completely filled. with hydraulic tluid.

From the foregoing description it will be apparentthat the energy absorption effected by the shock absorber is controlled rst by the orifices 30 and 34 and'V then bythe main controlY valve 40V in both directions of flow of uid between the cylinder chambers 32'and 33.

They spring 0A thatretains the valve 4t) on-its seat is a relatively light spring so that a relatively llow iluid pressure inthe cylinder chambers 32 and 33 will effect opening movement of thel valve piston dit. Thus, the piston 11y is relatively free to move in the working cylinder 10 of.` theshock absorber. Under this condition, rapid. movement of the axle-of the vehicle can take place rather freely since.y the resistance'to ow of hydraulic luidin they shock absorber*betweenthecylinder chambers 32 and 33' is lightly opposed by the, action of' the valve- 4t! as controlled: by the light compression spring 44. Such action of the shock absorber is satisfactory over aV choppy road condition until thev body of the vehicle begins to move. to cause no substantial body movement of the vehicle, the shock absorber willonlyfv lightly resist the action of the 'axle movements so that thesey movements can be largely absorbed bythe springsv of the vehicle.

This type of. action of the' shock absorber is permitted until thereaction of axle movements through the springsA are such as willV effect movement of the car body. AtV this time an' inertia responsive mechanism 75 `that is also responsiveto movements of the car body takes over control of` the shock. absorber to' provide for an increasev in the resistanceto flow offhydraulic fluidr between 'the cham bers 32 and. 33fofthe cylinder it@ sulicient tol providev thedesired damping effect or energy absorptionto retard lf the axle movement of. the vehicle is such as from a reservoir 81 and deliver the tluid under pressure into the discharge line 82. A pressure relief valve 83 is provided to bypass high pressure discharge from the pump 80 when the pressure increases above a desirable evel.

The Huid discharge line 82 from the pump 80 delivers fluid to a fluid flow control valve 90 provided in the inertia responsive mechanism 75. Controlled ow of fluid is delivered from the control valve 90 through the line 91 into the uid conducting passage 46 of the operating rod 12 that connects with a piston 11 of the shock absorber, whereby fluid under pressure can be delivered to the chamber 42 in the piston 11 of the shock absorber to react on the valve piston 40 to change the pressure value at which the valve 40 will be lifted from its seat as a result of the pressure reaction in the cylinder chambers 32 and'33 of the shock absorber.

From the foregoing description it is apparent that the fluid pressure control system for the valve piston 40 is isolated from the fluid in the shock absorber and may comprise any suitable source of pressure fluid adapted for control.

The inertia responsive mechanism 75 that includes the flow control valve 90, includes a body 95 that is adapted to be mounted on the car body of a motor vehicle. The body 95 has a chambered recess 96 forming a chamber 97 that is closed by a cover plate 98. A weight mass 99 is positioned in the chamber 97 and is normally disposed in a suspended position within the chamber 97 by means of the balance spring 101. Spring 100 acts as a bumper to limit upward movement of the weight mass 99.

The weight mass 99 has the property of tending to remain at rest unless it is acted upon by some external force, in this instance the movement of the body 95 relative to the mass 99. With theweight mass 99 tending to remain at rest the movement of the body 95 relative thereto effects signal operation of the inertia responsive mechanism 25.

The weight mass 99 is carried on the upper end of a valve stem 102 that is slidably positioned in the valve body 103 of the valve 90. t

The valve body 103 has a longitudinally extending valve bore 104 that receives the valve stern 102. The valve stem 102 is provided with the under cut portions 105 and 106 separated by the annular land portion. The annular land portion 107 is normally disposed in an enlarged chamber 108. The valve stem 102 is also providedwith the land portions 109 and 110 that are slidably disposed in the bore 104.

When the valve stem 102 of the valve 90 is in the position shown in Figure 1, lluid under pressure is free to pass from the discharge line 82 from the pump into the chamber 112 around the reduced diameter portion 106 and thence through the chamber 108 into the charnber 113 around the reduced diameter portion 105 of the stemand thence into the passage 114 in the body 95 and from there into the conduit 115 for return to 'the reservoir 81. The flow circuit just described thus provides for continuous circulation of fluid from the pump 80 through the control valve 90 and return to the reservoir 81.

` So long as the valve stem 102 of the valve 90 is disposed in the position shown in Fig. l, the fluid discharged from the pump 82 will have no effect upon the valve piston 40 in the piston 11 since the fluid is free to return to the reservoir. However, whenever the car body of the vehicle moves vertically relative to the road over which the vehicle is traveling there will be effected relative movement between the weight mass 99 and the body 95 `of the inertia responsive mechanism V75 since the weight mass 99 tends to remain stationary upon movement of the body 95 relative to the car axle. The rela' tive movement effected between the weight mass 99 and the body 95 will cause the valve stem 102 to move inY either an` upward vor a downward direction depending upon the initial direction of movement of the car body. However, in either movement of the valve stem 102 relative to the valve body 103 the land area 107 approaches either the chamber 112 or the chamber 113 to restrict the flow of fluid from the discharge line 812 to the reser.v

Voir return passage 114. This restriction of fiow of fluid causes the fluid pressure in the line 91 to increase and thereby increase the tluid pressure in the passage 46 of the operating rod 12 of the shock absorber which in turn increases the pressure of the hydraulic fluid in the cham ber 42 in the piston 11 of the shock absorber. As the pressure in the chamber 42 increases, the valve piston 40 is caused to seat more firmly upon its seat 41 in the head `28 of the piston 11. Thus, there will be required a greater pressure rise of the hydraulic fluid in either of the cylinder chambers 32 and 33 of the shock absorber cylinder 10 to raise the valve 40 from its seat 41 to allow passage of fluid through the opening 29 in the piston head 28, and thereby elfect a greater energy absorption in the shock absorber.

Since the degree of movement of the weight mass 99 in the inertia responsive device is directly proportional to the movement of the car body, the value of the pressure increase or pressure variation in the chamber 42 reacting on the Valve 40 will be directly proportional to vehicle body movement to obtain the desired value of energy absorption to damp the movement of the car body to the desired degree.

To prevent exceedingly rapid relative movement between the weight mass' 99 and the body 95 of the inertia responsive mechanism 75, the chamber 97 containing the weight mass 99 is connected with the reservoir return passage 114 by means of a passage 1204 whereby the chamber 97 is filled with hydraulic liquid circulated by the pump to damp reciprocable movement of the mass 99. The valve stem 102 has a passage 121 extending axially thereof to connect with the chamber 122 at the opposite end of the valve stem so that the valve is completely hydraulically balanced and thereby allow the weight mass 99 to be responsive solely to inertia action.

In Figure 2 there is illustrated a friction type of shock absorber adapted for use with the control system illustrated in Fig. 1 whereby the energy absorption of the v shock absorber is normally of relatively low value to permit relatively free axle motion, but which is controlled by the inertia responsive mechanism 75 to increase the energy absorption value of the shock absorber in response to movements of the body of a vehicle.

In the structural arrangement of the device of Fig. 2, the shock absorber comprises a cylinder 125 that is slidably engaged by a plurality of arcuately shaped friction elements 126. The friction elements 126 are carried upon arcuately shaped ring segments 12'7 each of which has the oppositely inclined faces 128 and 129. The friction elements 126 engage substantially the entire inner periphery of the cylinder 125, and the ring segments 127 form substantially a complete ring.

The ring segments 127 are carried upon an operating rod 130 that has a longitudinally extending passage 131 therein that corresponds to the passage 46 in the shock absorber illustrated in Fig. 1.

On the lower end ofthe operating rod l130 there is provided an annular enlargement 132. A reciprocable element 133 has the lowerrend portion 134 slidably disposed on the lower end of the operating rod 130 and the upper end portion 135 slidably disposed on the enlarged portion 132 that is xedly secured to the rod 130.

The ring segments 127 are confined between the annular face 136 on the lower end portion 134 of the member 133 and the angular face 137 on the head. 138 of the mounting stud threadedly received in `the lower end of the operating rod 130.

The operating rod 130 and the member 133 cooperate to form a fluid pressure receiving chamber 140 that is connected with the passage 131 iu the rod 130 by means aseaees ofa port passage 141. A light compression spring 142 is placed in the chamber 140 and normally urges the reciprocable member 133 toward the head 138 of the mounting stud to confine the ring segments 127 therebetween and lightly urge the friction elements lleradially outwardly against the inner periphery of the Wall of the cylinder 125.

The longitudinally extending passage 131 in the operating rod 130 is pro-vided with the conduitV connection fitting 145 that is adapted for connecting the uid pressure line 91a from the inertia responsive mechanism 75. Thus, delivery of fluid under varying pressure as controlled by the inertia responsive device 75 into the passage 131 and thus. into Vthe chamber 14d will cause the reciprocable member 133 to be urged toward the head 138 of the mounting stud with varying degrees of pressure, and thereby urge the friction elements l26'radially outwardly against the cylinder 125 with varying degrees of pressure to change the energy absorptin effectiveness of the energy absorbing device in direct proportion. to the movements of the car body. y

While the form of embodiment of the, invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted as may come within the scope of the claims which follow.

What is claimed is as follows:

l. A shock absorbing system for use on motor vehicles n to damp relative movements between the axle and the body of the vehicle, comprising in combination, a movement damping apparatus disposed between the car axle Vand body of'a vehicle and including an energy absorbing mechanism including resistance valve means resiliently held on its seat operable to eect energy absorption upon relative movement between the car axle and body on either compression or. rebound stroke of the movement damping apparatus, a source of fluid pressure operably' connected with said energy absorbing mechanism to apply lluid pressure to said val-ve means to retain it` on its seat resiliently to vary the energy absorption effectiveness of the. energy absorbing mechanism, and a lluid ow control means responsive to car body movement having fluid damping means utilizing said pressure fluid to damp relative movements between the axle and the body of the vehicle, comprising in combination, an hydraulic movement damping apparatus disposed between thecar axle and body of aV vehicle and including a cylinder having an energyl absorbing mechanism reciprocablev therein as carried on one end of a reciprocable operating rod projecting from one end of the cylinder, said rod and cylinder being respectively secured to the car body and axle. to effect said reciprocation of parts bythe relative movement het the axle body, resistance valve means in said energy absorbing mechanism resiliently held on its seat andcontrolling ow of hydraulic fluidbetween opposite sides o said energy absor-hing mechanism in either direction of movement of said mechanism in said cylinder and establishing one controlled rate of energy absorption of the mechanism and including lluid pressure actuated means operable to change the effect of the resiliently acting means to change the energyl absorption reffectiveness of the energy absorbing mechanism, saidrodhaving` a fluid conducting passage extending longitudinally thereof conductinguid, to said iiuid actuated means, asonrce of duid pressure con neetcd' with said rod; passage to apply duid pressure to said fluid pressure actuated means and thereby vary the resistance to'lluid Aflow in both directions through said valve means, and a fluid flow control means responsive all to car body movement to control flow of fluid pressureV from said source to said fluid pressure actuated means of said energy absorbing mechanism to changeV the resistance of said' valve means in proportion toV the degree of movement of the car body from a rest position.

3. A shock absorbing system for' use on motor vehiclesv to damp relative movements between the axle and the body of the Vehicle, comprising in combination, an hydraulic movement damping apparatus disposedl between the car axle and body of a vehicle and including a cylinder having a piston reciprocable thereinV as carried on one end of a reciprocable operating rod project'- ing from one end of the cylinder, said rod and cylinder being respectively secured to the car body and axle to effect said reciprocation of parts by the relative movement between the axle and the body, said'piston having a passage for llow of hydraulic fluid between opposite sides of said piston in either direction of movement' in said cylinder and having a chamber for receiving pressure fluid from a source external of the apparatus, resistance valve means in said chamber resiliently urged to close said passage and control flow of hydraulic lluid between opposite sides of said piston in either direction of movement of said piston in said cylinder, said' rod having a; fluid conducting passage extending longitudinally thereof for conducting duid to said chamber, a source of liuid pressure connected with said rod passage to supplyuid pressure to saidV chamber, and a fluid flow control means responsive to car body movement to control llowl offluidy pressure from said source t0 said'chamber for applica'- tion tosaid valve means to change its resistancel to-opening for ow of hydraulic iluid therethrough whereby to change the energy absorption effectiveness ofv said-'energyV absorbing mechanism in proportion to the'degreen ofV movementV of the car body from a rest position;

4. A shock absorbing system inr accordance with claim'v 3 in which the contro-l means comprises a body-having a valve means therein to control fluid ow from the said fluid pressure source to the said energy absorbing mechanism anda liuid damped weight massA operabl'y connected with the valve means foruactuation of the valve means and responsive to car body movement to effect opening of the valve means for flow of fluid pressure to the said energy absorbing mechanism on movement of the car body in either direction from a rest position.

5. A hydraulic shock absorber for use on motor vehicles, comprising, a cylinder closed 'at bothends, a piston reciprocable in said cylinder and mounted on the end ofv an operating rod projecting through one end of said cylinder, wall means aro-und said cylinder and the opposite end thereof formingV a reservoir chamber, a first valve means in the said opposite end of said cylinder responsive to pressure in said cylinder between said piston and the said opposite end thereof to openthe said valve means thereby, means forming a liuid liow passage from the said o-ne end of said cylinder to the said reservoir and controlled by the said' rst valve means to provide for Vtifow of hydraulic fluid from the said cylinder upon movement of theV said' piston toward the said one end of said cylinder, saidropposite end of said cylinder having a second valve means openable upon movement of said piston away from the said opposite end of said cylinder for llow of hydraulic fluid from the reservoir chamber into the cylinder between the saidl piston and the said opposite endy thereof, said piston having valve means therein controlling flow of hydraulic fluid through said piston in either of opposite directions, said piston having a fluid receiving chamber operably connected with the said valve means therein to change the lluidow characteristics of the valve means in the piston in response to changes in duid pressure in the said chamber,v

said rod having a fluid conducting passage extending,- longitudinally thereof for conduction of fluid Vunder pressure to said chamber.

6. A hydraulic shock -absorber in accordance with claim 5 in which the said valve means in said piston is a single valve having o-ne valve area exposed to fluid pressure in the cylinder between the piston and the said opposite end of the cylinder and another valve area exposed to fluid pressure in the said cylinder between said piston and the said one end of the cylinder whereby to eect resistance to opening of the said valve in either direction of flow of huid through the said piston.

7. A shock absorbing system for use on motor vehicles to damp relative movements between the axle and the body of the vehicle, comprising in combination, a movement damping apparatus disposed between the car axle and body of a vehicle and including an energy absorbing mechanism including resistance valve means resiliently held on its seat and operable to effect energy absorption upon relative movement between the car axle and body on either compression or rebound stroke of the movement damping apparatus, a source of fluid pressure operably connected with said energy absorbing mechanism to apply fluid pressure to said Valve means to retain it on its seat resiliently to vary the energy absorption eectiveness of the energy absorbing mechanism, and a fluid damped signal means disposed externally of the movement damping apparatus energizable on movement of the car body relative to the axle to control the fluid pressure applied from said source onto said valve means to vary the energy absorption effectiveness of the said mechanism in response to actuation of the signal means.

8. A hydraulic shock absorber for use on motor vehicles, comprising, a cylinder, a piston reciprocable in said cylinder and mounted o-n the end of an operating rod projecting through one end of said cylinder, wall means forming a reservoir chamber, a rst valve means in the opposite end of said cylinder responsive to pressure in said cylinder between said piston and the said opposite end thereof to open the said valve means thereby for flow of hydraulic fluid from the said cylinder upon movement of the said piston toward the said one end of said cylinder, said opposite end of said cylinder having a second Valve means openable upon movement of said piston away from the said opposite end of said cylinder for flow of hydraulic uid from the reservoir chamber into the cylinder between the said piston and the said opposite end thereof, said piston having valve means therein controlling ow of hydraulic fluid through said piston in either of opposite directions, said piston having a fluid receiving chamber operably connected with the said valve means therein to change the huid i'low characteristics of the valve means in the piston in response to changes in fluid pressure in the said chamber, said rod having' a uid conducting passage extending longitudinally thereof'for conduction of i'luid under pressure to said chamber, a source of fluid pressure connected with said rod passage to vary the iiuid iiow characteristics of the piston valve means, and a uid ow control means responsive to `car body movement having iluid damping means to retard movement of the control means to control the iluid pressure from said source to said uid receiving chamber to which the fluid flow characteristics of the piston valve means in relation to the movement of the car body form a rest position.

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